Well let me ask this. Considering the transfer function curve there is no response past about 50hz. Since many of us are using turnigy do you believe changing pwm faster than 100hz has any effect on flight? Because according to the data it wouldn't be possible. I am really interested to know your thoughts.

PT,
Sure. The first thing to recognize is that sometimes engineering data does not reflect operational reality, especially if it is mis-applied Also smaller multicopters under say about 30cm in diameter require faster updates of 400Hz+ to perform well. Conversely larger multicopter diameter frames can perform OK/well with slower ~100Hz-200Hz updates
I suppose if one compares the ~50Hz-100Hz poor multicopter performing Castle ESCs with the ~200Hz-300Hz non-modified Turnigy Plush series and re-brands, that would tell the tale. Based on most folks experiences, this has already been proved.

Well let me ask this. Considering the transfer function curve there is no response past about 50hz. Since many of us are using turnigy do you believe changing pwm faster than 100hz has any effect on flight? Because according to the data it wouldn't be possible. I am really interested to know your thoughts.

Well for starters the eRC has more programming options and above the 35A ESC they all come have switch mode BEC's with adjustable output voltage. Not saying these are way better or the end all be all of ESC's, just that they are proven to work well at 400Hz, have a good price, are available in the US readily, and are backed up with our support.

Jason

Has anyone run your eRC 120A opto esc on 6s pulling a constant 100A? I had looked at them but questioned the update rate. I have had plenty of trouble with heatsinks on the big ones.

PT,
Sure. The first thing to recognize is that sometimes engineering data does not reflect operational reality, especially if it is mis-applied Also smaller multicopters under say about 30cm in diameter require faster updates of 400Hz+ to perform well. Conversely larger multicopter diameter frames can perform OK/well with slower ~100Hz-200Hz updates
I suppose if one compares the ~50Hz-100Hz poor multicopter performing Castle ESCs with the ~200Hz-300Hz non-modified Turnigy Plush series and re-brands, that would tell the tale. Based on most folks experiences, this has already been proved.

It scares me when people say this kind of thing "sometimes engineering data does not reflect operational reality" You don't work at NASA do you.

Jesolins can you expand on "mis-applied".

Now back to my original question. If most people are using Turnigy with good results on most flight controllers, and considering the fact that the motor does not change speed above 50Hz (which would be a 100Hz throttle input), then why is it assumed that you have to have 200Hz, 400Hz, or 1000Hz.

I would really like your experienced thoughts on this past "it feels better" Remember that you can't simply change PWM update rate and see if the craft flies better. There are many other variables.

Oh and I have read the other threads on the subject. Honestly, the engineering figure-of-merit used for any system is Transfer Function. You can sweep and step and wobble all you want but in the end Sine in Sine out is what you have to measure.

PT,
No I have never directly worked for NASA, only USAF Flight test Yep I certainly would not have wanted to be the Aux rocket engineer at NASA...or the engineer that designed the pitot tube system on the B2 bomber, so you should be always be a bit scared as an engineer to be at your best...

Mis-applied refers to the lack of transfer of operational performance between the data you are posing and the way multicopters that use higher ESC update rates perform. Maybe I am preaching to the choir but do note that there are several frequencies used in the path from correctional inputs from the properly calibrated and PID applied gyros/accelerometers to FCB's, to ESCs, i.e. code loops, FCB PWM output frequency, ESC update frequency, Motor timing, ESC processor code loop timing and steps/smoothing and other "enhancement coding", all play a big part in the "real" operational performance off the multicopter.

This all applies to the fact that ESCs designed for multicopter use will ultimately be the best performers by at least a small margin in stability as the top multicopters like the Mikrokopter and X-BL have demonstrated. That said many folks are very satisfied with an extra oscillation or two in windy conditions and happy not to pay the premium for that extra performance

Again, we engineers should not ignore operational reality despite how we "read" the data, especially when they conflict.

It scares me when people say this kind of thing "sometimes engineering data does not reflect operational reality" You don't work at NASA do you.

Jesolins can you expand on "mis-applied".

Now back to my original question. If most people are using Turnigy with good results on most flight controllers, and considering the fact that the motor does not change speed above 50Hz (which would be a 100Hz throttle input), then why is it assumed that you have to have 200Hz, 400Hz, or 1000Hz.

I would really like your experienced thoughts on this past "it feels better" Remember that you can't simply change PWM update rate and see if the craft flies better. There are many other variables.

Oh and I have read the other threads on the subject. Honestly, the engineering figure-of-merit used for any system is Transfer Function. You can sweep and step and wobble all you want but in the end Sine in Sine out is what you have to measure.

I donīt understand many of the parameters and therms used on this threat or some of the links but... if the question is to get as high Hz value as possible from a ESC, some heads in Castle Creations co. must roll away. The can update the firmware to run at 100 hz and with the same effort in programing hours to do it for 200 hz or above. The will do it to run at 100 hz only because they canīt see any difference in the final airscrew reaction when using values above 100 hz and donīt want to waste energy in heat form if there is no advantage. That is so far what I was told from this history. CC has lost a piece of the market selling ESCs that are not usable in multirrotors and they will only adapt them to be 1/4 of the chinese speed at x8 times expensive? Are they crazy or their test are really representative and there is no need to increase speed beyond 100 hz but to work on other parameters as well?

Jesolins. My tricopter is much more stable than the one of the last video (modified pwm) and mine is based on std Futaba gyros with std output and not with the DS output enabled. May be I'm messing something but if my gyros work on std servo pwm and it's 50hz I can not provide faster changes than 50hz to the ESCs so as long as the ESC can follow this changes (under 50 hz) any speed of them above that value has no sense. What have I missed?

Hi El,
More info please. Do you have a similar indoor video showing stability? What ESCs are you using and what version of Futaba gyros and Tx/Rx are you using? How did you measure your Gyro and ESC PWM rates?
Cheers,
JimQuadrocopter and Tricopter Mega Link Index

Quote:

Originally Posted by elossam

Jesolins. My tricopter is much more stable than the one of the last video (modified pwm) and mine is based on std Futaba gyros with std output and not with the DS output enabled. May be I'm messing something but if my gyros work on std servo pwm and it's 50hz I can not provide faster changes than 50hz to the ESCs so as long as the ESC can follow this changes (under 50 hz) any speed of them above that value has no sense. What have I missed?

I believe (and please don't jump all over me if I get this all twisted) that the answer to this conundrum lies not in whether the motor can meaningfully respond to signalling above 100Hz but in the rate at which the FC is calculating new commands. By blasting the ESC with commands at 400Hz (or 1000Hz, or whatever) you ensure that when the ESC/motor does react, it's acting on the very latest command, not one that was issued "eons" ago. In other words, rather than discarding all the intermediate calculations that the FC does in 20ms (which is effectively what you're doing at 50Hz update rate), send as many of them as you can to the ESC and let it "do its best" with up-to-date commands.

Hi El,
More info please. Do you have a similar indoor video showing stability? What ESCs are you using and what version of Futaba gyros and Tx/Rx are you using? How did you measure your Gyro and ESC PWM rates?
Cheers,
JimQuadrocopter and Tricopter Mega Link Index

Hi Jesolins. this video was taken one year ago, just before I discovered how useful was to set the ATV from the TX at max and reduce the ammount of stick imput on the AP2000i mixer instead of reducing the ATV on the TX. That in therms of linear response to the stick orders that helps alot taming the machine while hovering. Tricoptero last flight. (1 min 38 sec)
Have no indoor videos but I wish to have an opportunity to fly one indoor. No wind breezes to disturb a relaxing flight. The high walls makes the slightly breeze to run rotors everywhere.

As you can see nothing but old stuffs. As far as I know the standar servo output of those gyros is 50 hz (20m/s) so if the ESC takes care of changes at that speed from the Gyros it will not send to the engine any different information even having a 400 hz comunication between ESC and engine, simply there is no new information to send. Have no idea about the PWM of the ESC but that doesnīt mind me in this case so long as the Gyro canīt provide more info or do it faster that what it was designed for , 20 m/s to work with std servos.

I built this tricopter as itīs only to demonstrate me and others time ago that a tricopter using std gyros and a mixer was perfectly doable and I was satisfied with the results. Please take it in mind when comparing it with recent hi-tech units.